/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.lwj.logger.io;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.SequenceInputStream;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * This class implements an output stream in which the data is written into a
 * byte array. The buffer automatically grows as data is written to it.
 * <p>
 * The data can be retrieved using <code>toByteArray()</code> and
 * <code>toString()</code>.
 * <p>
 * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this
 * class can be called after the stream has been closed without generating an
 * <tt>IOException</tt>.
 * <p>
 * This is an alternative implementation of the java.io.ByteArrayOutputStream
 * class. The original implementation only allocates 32 bytes at the beginning.
 * As this class is designed for heavy duty it starts at 1024 bytes. In contrast
 * to the original it doesn't reallocate the whole memory block but allocates
 * additional buffers. This way no buffers need to be garbage collected and the
 * contents don't have to be copied to the new buffer. This class is designed to
 * behave exactly like the original. The only exception is the deprecated
 * toString(int) method that has been ignored.
 * 
 * @author <a href="mailto:jeremias@apache.org">Jeremias Maerki</a>
 * @author Holger Hoffstatte
 * @version $Id: ByteArrayOutputStream.java 1021884 2010-10-12 18:49:16Z
 *          ggregory $
 */
public class ByteArrayOutputStream extends OutputStream {

	/** A singleton empty byte array. */
	private static final byte[] EMPTY_BYTE_ARRAY = new byte[0];

	/** The list of buffers, which grows and never reduces. */
	private final List<byte[]> buffers = new ArrayList<byte[]>();
	/** The index of the current buffer. */
	private int currentBufferIndex;
	/** The total count of bytes in all the filled buffers. */
	private int filledBufferSum;
	/** The current buffer. */
	private byte[] currentBuffer;
	/** The total count of bytes written. */
	private int count;

	/**
	 * Creates a new byte array output stream. The buffer capacity is initially 1024
	 * bytes, though its size increases if necessary.
	 */
	public ByteArrayOutputStream() {
		this(1024);
	}

	/**
	 * Creates a new byte array output stream, with a buffer capacity of the
	 * specified size, in bytes.
	 *
	 * @param size the initial size
	 * @throws IllegalArgumentException if size is negative
	 */
	public ByteArrayOutputStream(int size) {
		if (size < 0) {
			throw new IllegalArgumentException("Negative initial size: " + size);
		}
		synchronized (this) {
			needNewBuffer(size);
		}
	}

	/**
	 * Makes a new buffer available either by allocating a new one or re-cycling an
	 * existing one.
	 *
	 * @param newcount the size of the buffer if one is created
	 */
	private void needNewBuffer(int newcount) {
		if (currentBufferIndex < buffers.size() - 1) {
			// Recycling old buffer
			filledBufferSum += currentBuffer.length;

			currentBufferIndex++;
			currentBuffer = buffers.get(currentBufferIndex);
		} else {
			// Creating new buffer
			int newBufferSize;
			if (currentBuffer == null) {
				newBufferSize = newcount;
				filledBufferSum = 0;
			} else {
				newBufferSize = Math.max(currentBuffer.length << 1, newcount - filledBufferSum);
				filledBufferSum += currentBuffer.length;
			}

			currentBufferIndex++;
			currentBuffer = new byte[newBufferSize];
			buffers.add(currentBuffer);
		}
	}

	/**
	 * Write the bytes to byte array.
	 * 
	 * @param b   the bytes to write
	 * @param off The start offset
	 * @param len The number of bytes to write
	 */
	@Override
	public void write(byte[] b, int off, int len) {
		if ((off < 0) || (off > b.length) || (len < 0) || ((off + len) > b.length) || ((off + len) < 0)) {
			throw new IndexOutOfBoundsException();
		} else if (len == 0) {
			return;
		}
		synchronized (this) {
			int newcount = count + len;
			int remaining = len;
			int inBufferPos = count - filledBufferSum;
			while (remaining > 0) {
				int part = Math.min(remaining, currentBuffer.length - inBufferPos);
				System.arraycopy(b, off + len - remaining, currentBuffer, inBufferPos, part);
				remaining -= part;
				if (remaining > 0) {
					needNewBuffer(newcount);
					inBufferPos = 0;
				}
			}
			count = newcount;
		}
	}

	/**
	 * Write a byte to byte array.
	 * 
	 * @param b the byte to write
	 */
	@Override
	public synchronized void write(int b) {
		int inBufferPos = count - filledBufferSum;
		if (inBufferPos == currentBuffer.length) {
			needNewBuffer(count + 1);
			inBufferPos = 0;
		}
		currentBuffer[inBufferPos] = (byte) b;
		count++;
	}

	/**
	 * Writes the entire contents of the specified input stream to this byte stream.
	 * Bytes from the input stream are read directly into the internal buffers of
	 * this streams.
	 *
	 * @param in the input stream to read from
	 * @return total number of bytes read from the input stream (and written to this
	 *         stream)
	 * @throws IOException if an I/O error occurs while reading the input stream
	 * @since Commons IO 1.4
	 */
	public synchronized int write(InputStream in) throws IOException {
		int readCount = 0;
		int inBufferPos = count - filledBufferSum;
		int n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
		while (n != -1) {
			readCount += n;
			inBufferPos += n;
			count += n;
			if (inBufferPos == currentBuffer.length) {
				needNewBuffer(currentBuffer.length);
				inBufferPos = 0;
			}
			n = in.read(currentBuffer, inBufferPos, currentBuffer.length - inBufferPos);
		}
		return readCount;
	}

	/**
	 * Return the current size of the byte array.
	 * 
	 * @return the current size of the byte array
	 */
	public synchronized int size() {
		return count;
	}

	/**
	 * Closing a <tt>ByteArrayOutputStream</tt> has no effect. The methods in this
	 * class can be called after the stream has been closed without generating an
	 * <tt>IOException</tt>.
	 *
	 * @throws IOException never (this method should not declare this exception but
	 *                     it has to now due to backwards compatability)
	 */
	@Override
	public void close() throws IOException {
		// nop
	}

	/**
	 * @see java.io.ByteArrayOutputStream#reset()
	 */
	public synchronized void reset() {
		count = 0;
		filledBufferSum = 0;
		currentBufferIndex = 0;
		currentBuffer = buffers.get(currentBufferIndex);
	}

	/**
	 * Writes the entire contents of this byte stream to the specified output
	 * stream.
	 *
	 * @param out the output stream to write to
	 * @throws IOException if an I/O error occurs, such as if the stream is closed
	 * @see java.io.ByteArrayOutputStream#writeTo(OutputStream)
	 */
	public synchronized void writeTo(OutputStream out) throws IOException {
		int remaining = count;
		for (byte[] buf : buffers) {
			int c = Math.min(buf.length, remaining);
			out.write(buf, 0, c);
			remaining -= c;
			if (remaining == 0) {
				break;
			}
		}
	}

	/**
	 * Fetches entire contents of an <code>InputStream</code> and represent same
	 * data as result InputStream.
	 * <p>
	 * This method is useful where,
	 * <ul>
	 * <li>Source InputStream is slow.</li>
	 * <li>It has network resources associated, so we cannot keep it open for long
	 * time.</li>
	 * <li>It has network timeout associated.</li>
	 * </ul>
	 * It can be used in favor of {@link #toByteArray()}, since it avoids
	 * unnecessary allocation and copy of byte[].<br>
	 * This method buffers the input internally, so there is no need to use a
	 * <code>BufferedInputStream</code>.
	 * 
	 * @param input Stream to be fully buffered.
	 * @return A fully buffered stream.
	 * @throws IOException if an I/O error occurs
	 * @since Commons IO 2.0
	 */
	public static InputStream toBufferedInputStream(InputStream input) throws IOException {
		@SuppressWarnings("resource")
		ByteArrayOutputStream output = new ByteArrayOutputStream();
		output.write(input);
		return output.toBufferedInputStream();
	}

	/**
	 * Gets the current contents of this byte stream as a Input Stream. The returned
	 * stream is backed by buffers of <code>this</code> stream, avoiding memory
	 * allocation and copy, thus saving space and time.<br>
	 * 
	 * @return the current contents of this output stream.
	 * @see java.io.ByteArrayOutputStream#toByteArray()
	 * @see #reset()
	 * @since Commons IO 2.0
	 */
	private InputStream toBufferedInputStream() {
		int remaining = count;
		if (remaining == 0) {
			return new ClosedInputStream();
		}
		List<ByteArrayInputStream> list = new ArrayList<ByteArrayInputStream>(buffers.size());
		for (byte[] buf : buffers) {
			int c = Math.min(buf.length, remaining);
			list.add(new ByteArrayInputStream(buf, 0, c));
			remaining -= c;
			if (remaining == 0) {
				break;
			}
		}
		return new SequenceInputStream(Collections.enumeration(list));
	}

	/**
	 * Gets the curent contents of this byte stream as a byte array. The result is
	 * independent of this stream.
	 *
	 * @return the current contents of this output stream, as a byte array
	 * @see java.io.ByteArrayOutputStream#toByteArray()
	 */
	public synchronized byte[] toByteArray() {
		int remaining = count;
		if (remaining == 0) {
			return EMPTY_BYTE_ARRAY;
		}
		byte newbuf[] = new byte[remaining];
		int pos = 0;
		for (byte[] buf : buffers) {
			int c = Math.min(buf.length, remaining);
			System.arraycopy(buf, 0, newbuf, pos, c);
			pos += c;
			remaining -= c;
			if (remaining == 0) {
				break;
			}
		}
		return newbuf;
	}

	/**
	 * Gets the curent contents of this byte stream as a string.
	 * 
	 * @return the contents of the byte array as a String
	 * @see java.io.ByteArrayOutputStream#toString()
	 */
	@Override
	public String toString() {
		return new String(toByteArray());
	}

	/**
	 * Gets the curent contents of this byte stream as a string using the specified
	 * encoding.
	 *
	 * @param enc the name of the character encoding
	 * @return the string converted from the byte array
	 * @throws UnsupportedEncodingException if the encoding is not supported
	 * @see java.io.ByteArrayOutputStream#toString(String)
	 */
	public String toString(String enc) throws UnsupportedEncodingException {
		return new String(toByteArray(), enc);
	}

}
